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Biomedical subjects

K Yagi

Publications and source records attributed to K Yagi.

At least 703 records · Page 39Linked to original sources
PubMed1978

Reaction of linoleic acid hydroperoxide with thiobarbituric acid.

The linoleic acid hydroperoxide obtained by enzymatic peroxidation of linoleic acid was found to react with thiobarbituric acid to yield a red pigment. The optimum pH for the reaction was found to be 4.0. In the early stages of peroxidation of linoleic acid, thiobarbituric acid value, the amount of conjugated diene, oxygen consumption, and peroxide value were in parallel with one another. The data were compared with those on peroxidation of linolenic acid and arachidonic acid.

Chemical Phenomena↗
PubMed1978

Studies on the immune response in chickens I. Effect of various immunization procedures on the primary and secondary antibody responses to bovine serum albumin.

Antibody response and generation of immunological memory in chickens after stimulation by bovine serum albumin (BSA) were investigated. A single intravenous injection of BSA induced a relatively high primary antibody response but failed to generate definite memory for the secondary antibody response. Variation in antigen dosage and the time interval between antigen injections did not affect significantly the levels of the primary and secondary antibody responses. The immunogenicity of deaggregated BSA in chickens was as potent as that of aggregated BSA. Soluble adjuvants such as the capsular polysaccharide of Klebsiella pneumoniae, cell wall lipopolysaccharide of Salmonella enteritidis and cell wall peptidoglycan of Staphylococcus epidermidis exhibited little enhancing effect on antibody response and memory. However, stimulation of chickens by BSA emulsified in Freund's adjuvant enhanced generation of memory. Repeated injection of BSA alone also showed a similar effect. It seems likely therefore that in chickens continous antigenic stimulation is required for generation of definite memory. From the present results it has been concluded that the characteristics of the immune response of chickens to BSA resemble those of mammals to T-independent antigens.

Animals↗
PubMed1977

Permeability of amino acids into liposomes.

1. A simple and rapid assay for the measurement of permeability of amino acids into liposome membrane was carried out by using the liposomes trapping D-amino acid oxidase (D-amino acid: O2 oxidoreductase (deaminating), EC 1.4.3.3) inside the membrane. 2. Permeability of amino acids into liposomes depended on the lipid composition of the membrane. Permeability of amino acids into phosphatidylcholine-cholesterol liposomes depended critically on temperature. 3. Permeability also depended on the structure of amino acids. The order of permeability was norvaline greater than isoleucine greater than leucine greater than phenylalanine greater than tryptophan greater than methionine greater than tyrosine, valine greater than threonine greater than serine greater than alanine greater than glycine.

Amino Acids↗
PubMed1977

Monoamine oxidase in developing chick retina.

The developmental changes in monoamine oxidase (MAO) activities towards 5-hydroxytryptamine (5-HT) and beta-phenylethylamine (PEA) in chick retina were investigated. The whole pattern of the developmental changes in MAO activity towards 5-HT was similar to that towards PEA, even though the activity towards 5-HT was much lower than that towards PEA during the period from the 12th day of incubation to the 14th day after hatching. The MAO activities on the 12th day of incubation were low and increased remarkably until the 18th day of incubation. Then they remained unchanged until the 7th day after hatching; therefore, they decreased. The activities measured on the 14th day after hatching are on the same level as those of an adult. The multiplicity of MAO in the retinae of a chick on the 12th day of incubation and of an adult was also studied with specific inhibitors. The result showed that the major part of MAO in chick retina is type B enzyme; that type A MAO in the retina of an adult is, however, relatively higher than that in the retina of the embryo on the 12th day of incubation. It was found that an appreciable amount of MAO activity towards 5-HT in chick retina is due to type B MAO.

Age Factors↗
PubMed1977

Lipoperoxide level of the retina of chick embryo exposed to high concentration of oxygen.

To approach the mechanism of degeneration of the retina in retinopathy of prematurity, a model experiment using chick embryo was carried out. Upon exposing chick embryo at various stages to a high concentration of oxygen at 2 atm pressure, lipoperoxide levels of both the blood and the retina were elevated. The change in lipoperoxide level of the liver was not significant, except for a slight increase at the 9th day of incubation. Upon exposing chick embryo of the 14th day to high concentration of oxygen at ambient pressure, lipoperoxide levels of both the blood and the retina were elevated at 6 h and 12 h of exposure, but significant change was not observed in the lipoperoxide level of the liver.

Animals↗
PubMed1977

A fluorometric assay for beta-phenylethylamine in human urine.

A sensitive and specific method for the fluorometric determination of beta-phenylethylamine (PEA) in human urine is described. PEA in urine was separated from phenylalanine and 5-hydroxytryptamine by n-heptane extraction, and determined by the ninhydrin reaction in the presence of L-leucyl-L-alanine. Using this method, the amounts of free PEA in urine samples of normal subjects and schizophrenics were measured. Normal subjects excreted 15.9 +/- 6.4 microgarm/day of free PEA, and chronic schizophrenics 9.3 +/- 2.7 microgram/day of free PEA. In normal subjects, the highest excretion of free PEA was observed in the period from 4:00 p.m. to 12:00 p.m. in a day.

Adult↗
PubMed1977

Effect of hydrophobic probes on the higher structure of D-amino acid oxidase.

1. The holoenzyme of D-amino acid oxidase [D-amino acid: O2 oxidoreductase (deaminating), EC 1.4.3.3] was found to combine with 1-anilinonaphthalene-8-sulfonate without liberation of its coenzyme, FAD. No energy transfer interaction was found to occur between the bound dye and FAD of the holoenzyme. On the other hand, when the apoenzyme was bound to the dye and then to FAD, energy transfer interaction between the bound dye and bound FAD was observed. In both cases, the dye competes with the substrate, D-alanine. It is concluded that the dye bound to the holoenzyme is oriented in such a special manner that the mutual orientation factor between the dye and FAD becomes very small in magnitude. 2. When the apoenzyme combined with the dye, the monomer-dimer equilibrium of the apoenzyme shifted towards the dimer. On the other hand, 4-monobenzoylamido-4'-aminostilbene-2,2'-disulfonate combined with the apoenzyme to induce monomerization.

Alanine↗
PubMed1977

Effect of alcohols on the structure and function of D-amino-acid oxidase.

The absorption spectrum of D-amino-acid oxidase (D-amino-acid:oxygen oxidoreductase (deaminating), EC 1.4.3.3) was significantly perturbed by various alcohols; typical fine structures were observed in the visible absorption bands, accompanied by blue shifts of the peaks. Both fluorescence intensity and fluorescence polarization were increased upon the addition of alcohols, indicating that the coenzyme is not liberated from the apoenzyme but the hydrophobicity of the environment of the enzyme-bound flavin is increased. Upon the addition of alcohols, the circular dichroism of the enzyme was markedly modified in the visible and near-ultraviolet regions, while that of the apoenzyme in the near- and far-ultraviolet regions was scarcely modified, indicating a change in the interaction between the flavin coenzyme and protein. Both the apparent maximal velocity and the apparent Michaelis constant of the enzyme were increased by the addition of alcohols. The presence of alcohols tends to dissociate the dimer of this enzyme into the monomer, but the dissociation does not fully explain the increase in the maximal velocity of the enzyme by alcohols, because the increase in the maximal velocity caused by alcohols is larger than that expected from the dissociation. Since the rate of formation of the purple intermediate was decreased by alcohols in both the dimer and the monomer, the increase in the maximal velocity could be ascribed to an increase in the rate of dissociation of the enzyme-product complex. This increase could be ascribed to the protein conformational change, which is probably provoked by combination of alcohols with the enzyme at a locus other than that for substrate binding.

1-Propanol↗